Here's a link to a thread on XDA where ISIS is working on a Maxx. I haven't done this yet to my phone, and it's not clear from the thread whether the Secure Element SIM is required -- I heard it was only available in the two ISIS test markets, SLC & San Antonio.
I do have to agree with doogald that payment by NFC doesn't really bring much to the table. That said, I've been a huge fan and regular user of Google Wallet on my VZW Gnex since launch, even signed up for the Citi MasterCard that was originally the only credit card to work with that service.
Peet's Coffee, 7-Eleven, Walgreens, my auto mechanic -- I'd use that thing everywhere I could. Does it really offer any advantages over a card swipe? Not really. Having to unlock the phone and enter my GW PIN in some ways made it more inconvenient, and occasionally the clerk or the reader would be problematic.
But in theory, there's an added element of security, since my card isn't out there to be read and later replicated. But that's more of a threat at gas stations (which I haven't seen take NFC payments), or in restaurants where the server takes the card back behind the counter (I'm not handing over my phone!).
My last Google Wallet NFC transaction? Verizon Wireless, to purchase my Maxx. "Cool, I've never seen that before" said the Verizon girl. Gosh, really? I wonder why. :/